Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$197.67	3.222%	$204.0389	$204.04	$204.05	$204.00
Purchase #2	$142.27	8.832%	$154.8353	$154.84	$154.85	$154.80
Purchase #3	$36.71	9.860%	$40.3296	$40.33	$40.35	$40.30
Purchase #4	$172.67	13.828%	$196.5468	$196.55	$196.55	$196.50
Purchase #5	$204.52	10.266%	$225.516	$225.52	$225.50	$225.50
Purchase #6	$174.32	11.689%	$194.6963	$194.70	$194.70	$194.70
Purchase #7	$153.70	7.644%	$165.4488	$165.45	$165.45	$165.40
7 purchase totals =	$1,081.86		$1,181.4117	$1,181.43	$1,181.45	$1,181.20